The name atop that bombshell: Jeannie Rhee, whom Mueller recruited from WilmerHale, the law firm where he has worked since he stepped down as FBI director in 2013.

The former federal prosecutor is known to her colleagues, as one told me, as “an absolute ace trial lawyer—one of the best to ever come out of the US Attorney’s Office.” Mueller evidently agreed, asking her to join perhaps the greatest assemblage of prosecutorial talent ever gathered at the Justice Department.

It’s a hire that paid immediate dividends.

Monday morning’s Manafort indictment alone would have been big news, not least because the 31-page document accompanying it laid out a lavish lifestyle of Range Rovers, Mercedes, men’s clothing, rugs, and luxury condos allegedly financed with income hidden from the IRS and funneled through a Matryoshka doll of international front companies.

But even as the White House was beginning to put out talking points—and the president himself was tweeting—that Manafort was a “bad guy” but his conduct was unrelated to the 2016 campaign, Mueller’s team produced its surprise second act.

They had another case that went to the heart of whether the Trump campaign had attempted to collude with Russia officials during the 2016 campaign.

And the suspect had already been arrested.

And he had already pleaded guilty.

And he was cooperating.

Until today, Papadopoulos had seemed a bit player in a year-long scandal that starred Manafort, former national security adviser Mike Flynn, and even the president’s own son, Donald Trump Jr.

He is a bit player no longer.

Papadopoulos’ exact level of engagement in the Trump campaign became an instant point of debate on Monday; the White House downplayed him as a low-level “volunteer,” even as photos circulated of him sitting at a table with Trump and just two people away from Jeff Sessions.

Mueller’s bombshell announcement: Papadopoulos had worked with people he knew to be involved at a high level with the Russian government in an attempt to obtain “dirt” on Hillary Clinton, notably thousands of stolen emails. He had worked to “arrange a meeting between the Campaign and the Russian government officials,” and had otherwise endeavored through multiple rounds of contact with both Russian-linked individuals and with the Trump campaign to coordinate gaining access to material that would harm Trump’s Democratic opponent. At least one of his contacts was with a woman he believed—evidently incorrectly—was a niece of Russian president Vladimir Putin.

Then he lied about that effort to the FBI—a violation of 18 U.S.C., Section 1001, and one of the easiest traps for federal investigators to spring on targets who think that the FBI is less savvy than it is—and made ham-handed attempts to cover up those lies by deleting social media profiles and changing his telephone number.

The Papadopoulos plea will likely be seen as the point of no return.

The allegations date back to March 2016—just as the GOP primaries were wrapping up with the surprise victory of a New York real estate mogul and reality TV host over a field of 16 other more traditional candidates. At that point, Mueller’s court documents lay out—and, according to his plea agreement, Papadopoulos has admitted the documents are “true and accurate” descriptions of his involvement—how Papadopoulos made contact with a London-based professor known to have Russian connections who suddenly developed a “great interest” in Papadopoulos after learning he was advising Trump.

The contact continued for months, with Papadopoulos even evidently speaking with an official from Russia’s ministry of foreign affairs in an attempt to coordinate an “off-the-record” meeting between the campaign and Russian officials. The effort appears to have petered out unsuccessfully.

When the FBI asked him about that contact in January 2017—a date that makes clear that the FBI was hard at work tracking the Trump campaign’s contact with Russia even within days of the inauguration—Papadopoulos made numerous false statements, later proven through the FBI’s follow-on investigation. He was arrested in July and cooperated with investigators at that point; often suspects find that they have little choice but to cooperate once they’re caught in a lie that could net five years in federal prison on its own, or up to a $250,000 fine. He pleaded guilty weeks ago, working with prosecutors Rhee, Andrew Goldstein, and Aaron Zelinsky, but the case was only unsealed today.

Papadopoulos’ actions may not be “collusion,” but it’s a start.

Mueller has established, in dry but nonetheless dramatic language laid out in a federal court document, that there were ties between the Trump campaign and officials in Russia.

It’s just one of many mysteries still for Mueller to solve and share.

In fact, it turns out that the same day—January 27, 2017—Papadopoulos lied about his contacts with Russian officials to FBI investigators, President Trump asked since-fired FBI director James Comey for a loyalty pledge at the White House. Are the two acts related in some way? We don’t know yet.

Papadopoulos might shine yet more light on the campaign—and his case serves as a warning to everyone else that they had better cooperate as well. After all, in today’s court filing, the special counsel recommended just zero to six months in prison and a fine somewhere between $500 and $9,500—far better than he might have otherwise faced.

When the final history of the Trump campaign is written—if, that is, we avoid nuclear war with North Korea and there’s anyone left alive to write it—the Papadopoulos plea will likely be seen as the point of no return, the moment when a political story that had been kept alive for months with rumors and speculation, a story that the President himself had dismissing as a nothingburger as late as Monday morning, achieved an inescapable momentum.

Now the country is left awaiting Mueller’s answer to the even larger question: How far did the ties extend, and who was involved?

I wrote a guide earlier explaining how to think about the charges, including five rules for how federal investigations tend to unfold. But developments in the Papadopoulos and Manafort cases Monday—unique among perhaps all previous cases in the Justice Department—provide some corollaries for us to consider going forward.

Call them the “Mueller Rules,” governing what we now know about how Mueller will operate as special counsel:

1) Mueller will be comprehensive. The court documents unsealed Monday are exactly what you would expect from a talented team of experienced prosecutors. Mueller’s hallmark at every stage of his career has been his intense focus on detail, grilling his staff like they were hostile witnesses under cross-examination.

In Monday’s cases, they started with essentially with low-hanging fruit, places where black-and-white documents could guide their way, or statements could be easily disproven. The Manafort case is complex, but also relatively straightforward, traceable through bank records, wire transfers, and payments. The Papadopoulos case was, too. He’s not being prosecuted for his attempt at conspiracy against the United States, which would be complicated to argue. He made a statement to the FBI, and they had documents that indicated it was false.

2) Mueller will be tenacious, using every tool in the toolbox. When other potential players in this widening scandal read today’s indictments, a couple of things will stand out. The criminal charge of being an unregistered foreign agent—a so-called “FARA violation”—against Paul Manafort is a rare crime, used just four times (all successfully) in the last decade. Normally, it’s allowed to be just a civil penalty, so the fact that Mueller has deployed it as a criminal one means he’s going for maximum leverage.

Ditto for backing Papadopoulos into pleading guilty to a false statements charge; it’s often a prosecutor’s favorite way to force compliance and cooperation with a potential witness. Former national security adviser Mike Flynn knows he has some legal exposure on FARA too; he retroactively filed paperwork this year to clean up his previous statements and declare his work on behalf of Turkey. Mueller’s Manafort indictment tucked a message between the lines: That may not be enough to escape the glare.

3) There’s much more to come. Buried in the depths of the Papadopoulos plea is this line: “These facts do not constitute all of the facts known to the parties concerning the charged offense.” In some ways, it’s boilerplate for a federal indictment. In this case, we know it isn’t. The cases unveiled Monday represent only tiny corners of the rocks Mueller has been turning over. There’s still the Trump Tower meeting that involved Manafort and Donald Trump Jr. There’s still Russia’s social media ad buys. There’s still the hacking of the DNC and the theft of Clinton campaign chairman John Podesta’s emails. There are other suspicious meetings with Russian officials, including those by Attorney General Jeff Sessions, himself.

The investigation will go on for quite some time. The charges against Manafort alone wouldn’t likely go to trial for the better part of a year—if they go to trial at all. There are likely to be superseding indictments, with updated charges, and Manafort, a central player to many parts of the Trump campaign, has 12 new reasons to talk to Mueller’s investigators that he didn’t have on Friday. At 68, Manafort has to realize that even a relatively short federal prison sentence might end up being a life sentence—and he doesn’t seem like the type who would like to die in jail.

4) Mueller’s working multiple avenues at once. For all of the political teeth-gnashing, this case is going to be just like any other federal investigation. In dismantling a criminal organization and unraveling a major case, the FBI and Justice Department are trained to start with peripheral players—begin at the bottom, and work your way to the top. Mueller is pursuing that strategy on two fronts. He’s starting at the top, with Paul Manafort, but focusing on the peripheral issues surrounding Manafort’s businesses going back to even before Barack Obama was elected to the White House. And he’s also starting at the periphery of the campaign itself, with minor figures like Papadopoulos.

5) Mueller’s running a leak-free ship—and he knows more than we think. Given how closely watched his investigation has been by nearly every corner in Washington—people are even sending in random sightings of him to POLITICO’s Playbook tipsheet after spotting him walking alone on the street—Mueller has tricks up his sleeve. The Papadopoulos arrest three months ago (!) was nowhere on Washington’s radar. And even as every reporter in Washington devoted the weekend to chasing who would be indicted today, we didn’t know it was Manafort until he left his house on the way to the FBI’s Washington Field Office.

Capitol Hill Republicans and talking heads on Fox News have wailed over leaks from the special counsel office—and there’s quite the precedent in Washington for just that. Ken Starr’s Whitewater case was all but an open book. But Monday proved what reporters in Washington have known all fall: Mueller is playing close to the vest. Leaks, such as they’ve come, have primarily stemmed from defense attorneys, Capitol Hill, and other players outside of Mueller’s orbit. The former FBI director, always known for keeping his head down and eschewing the media spotlight, continues to do just that. In a city where it seems increasingly hard to keep anything secret, he kept two major ones.

Altogether, it’s enough to leave everyone involved in the Trump campaign wondering: What other secrets does Mueller know? And: Just who else might be cooperating?

Garrett M. Graff (@vermontgmg) is a contributing editor for WIRED and the author of The Threat Matrix: Inside Robert Mueller’s FBI. He can be reached at garrett.graff@gmail.com.